Xresources, Xt, and beyond

[Ivan Shmakov]

>>>>> Aaron W Hsu <arc...@sacrideo.us> writes:
>>>>> Mike Spencer <m...@bogus.nodomain.nowhere> writes:

[Cross-posting to news:comp.windows.x.intrinsics and
news:comp.windows.x, and setting Followup-To: there, for the
discussion is hardly Slackware-specific.]

>> Cool. I didn't know you could do that. I still don't get the syntax.

> There are alot of powerful things about X that have been mostly
> forgotten by more "modern" toolkits.

Sad but true.

[...]

> In general, there is a hierarchy of tech that adds to the basic Xlib,
> such as Xt, Motif, and so forth. If your application uses only Xlib,
> then you can only access properties that Xlib provides or that were
> provided explicitly by the application. On the other hand, if your
> application is written in Motif, which is a layer on top of Xt, which
> is a layer on top of Xlib, then you can access all the properties
> that a widget inherits from Xt and Xlib, in addition to any specific
> Motif properties that a widget may have.

It was my understanding that Xlib doesn't provide any widgets,
and that the core widgets are provided by Xt. On top of which
there were a variety of toolkits, such as Xaw, Xaw3d, LessTif,
and (non-free) Motif.

> Unfortunately, other toolkits like GTK or Qt break this X
> abstraction, and tend to reimplement this functionality in their own,
> more complicated and less regular form.

One possible explanation to this is that these toolkits were
intended to be usable outside of X. The other is that,
unfortunately, there're a number of cases when the X resources
fail to do the thing.

For instance, if the colors, or a font face, is specified once
in app-defaults, like:

App*foreground: wheat
App*background: darkslategray

it's trivial to override this setting via command line, like:

$ app -xrm '*foreground: navyblue' -xrm '*background: gray' &

Unfortunately, there's no easy way to override the colors of an
application whose widgets are colored differently, like:

App*foreground: wheat
App*background: darkslategray
App.Widget.foreground: green
App.Widget.background: black

There, the command above will force the colors for all the
application widgets except the one of the Widget class.

Tk seemingly gets it right, by extending X resources with
priorities. Still, the X server resource database is just one
of these priorities from the Tk's point of view.

[...]

> All this reinventing the wheel is one of the reasons that I like to
> stick with Motif applications a lot. For example, I recompile Emacs
> to use Motif instead of GTK, which makes it easier for me to tweak
> with Xresources,

FWIW, Debian includes a Emacs binary linked with Xaw3d.

> or I just use the NEdit text editor, which is also written in Motif.

[...]

--
FSF associate member #7257

[Aaron W. Hsu]

Ivan Shmakov <onei...@gmail.com> writes:

> It was my understanding that Xlib doesn't provide any widgets,
> and that the core widgets are provided by Xt. On top of which
> there were a variety of toolkits, such as Xaw, Xaw3d, LessTif,
> and (non-free) Motif.

This is my understanding as well, except that Motif is a little better than
non-free, and IMO should be used instead of LessTif on FOSS machines.

> The other is that, unfortunately, there're a number of cases when the
> X resources fail to do the thing.

> For instance, if the colors, or a font face, is specified once
> in app-defaults, like:

> App*foreground: wheat
> App*background: darkslategray

> it's trivial to override this setting via command line, like:

> $ app -xrm '*foreground: navyblue' -xrm '*background: gray' &

> Unfortunately, there's no easy way to override the colors of an
> application whose widgets are colored differently, like:

> App*foreground: wheat
> App*background: darkslategray
> App.Widget.foreground: green
> App.Widget.background: black

> There, the command above will force the colors for all the
> application widgets except the one of the Widget class.

> Tk seemingly gets it right, by extending X resources with
> priorities. Still, the X server resource database is just one
> of these priorities from the Tk's point of view.

Xresources are certainly not perfect. I think the problem here is that
it is not good style for applications to be encoding colors in their own
app-defaults file. However, it is possible to replace or override an
app-defaults file if so desired, but it is more work than just setting
some resources in Xresources.

I have some applications that work like this, and I have switched their
themes successfully, so I think that mostly tweaks are necessary to make
Xresources better, rather than reimplementing the whole system.

The nice thing about X resources is that they provide a universally useful
means of setting properties, and I hate to see toolkits duplicating this
functionality in ways that makes it impossible to work across toolkits.

--
--
Aaron W. Hsu | arc...@sacrideo.us | http://www.sacrideo.us
Programming is just another word for the lost art of thinking.